You may also like

Choose any three by three square of dates on a calendar page.
Circle any number on the top row, put a line through the other
numbers that are in the same row and column as your circled number.
Repeat this for a number of your choice from the second row. You
should now have just one number left on the bottom row, circle it.
Find the total for the three numbers circled. Compare this total
with the number in the centre of the square. What do you find? Can
you explain why this happens?

Back to the Planet of Vuvv

Stage: 3 Challenge Level:

On the planet Vuvv there are two sorts of creatures. The Zios
have $3$ legs and the Zepts have $7$ legs.

So naturally there are two forms of counting on Vuvv - Zios
count in base $3$ and Zepts count in base $7$.

When observed, the creatures on this planet lie on the ground
with their legs in the air, so that legs, not bodies, can be most
easily counted.

One day four of these creatures, two Zios and two Zepts, sat on
the summit of a hill to count the legs of the creatures they could
see. One looked to the East, one to the West, one to the South and
one to the North.

The creature looking to the West wrote down its number:
$122$

The creature looking to the East wrote down its number: $22$

The creature looking to the South wrote down its number:
$101$

The creature looking to the North wrote down its number:
$41$

In which direction are the $2$ Zios looking and in which
directions are the $2$ Zepts looking?

The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities
can be found here.